Pneumatic spring



Jan. 7, y1930.

W. B. CIHAPMAN PNEUMATIC SPRING Filed April 23, 1925 vwentoz PietedJm. 7, 1930 *"-UN'ITED s'luklvlsz- S- PATENT orFlcE winmx n. CHAPMAN, or :Monson lmuertas, maw Yom:

rnnunarrc arma I application mea April 2s, .serial Nofsaaas. g

neumatic The invention relates to a housin spring consisting of piston an tv. een for the lieving mechanical shocks transmitted from one member to the other. The spring is designed primarily as a support for vehicle bodies, thus serving as a substitute for the metallic springs usually employed for such purposes. v

One important object .of the invention is to provide a spring of the above type wherein the pressure in the pneumatic cushion which supports the load will be automatically increased by the addition of fluid to 'such cushion during the compression stroke so that air and liquid employed t an increase in the load carried is soon compensated forby a corresponding increase in the pressure of the sustaining cushion.

' In another aspect the invention 'involves the use of what may be termed complemen` tary air chambers on opposite sides of the piston member and the transfer of fluid under pressure from one chamber to the other in accordance with load conditions, thus securing a double balancing effect in that the building up of pressure on one side of the piston involves a drop in pressure on the other side which is cumulative in effect. Hence it is necessary to transfer but a minimum amount f f fluid to obtain a maximum amount of efect.

Another feature of the invention is the employment of liquid in the spring in such manner that the How of liquid induced by relative motion between the piston andfcylinder, causes air to be aspirated into the sustaining air cushion during compression strokes. The liquid also serves to dampen the excessive resiliency of the air, and acts as a lubricant to keep the packing in pro er condition.

Speaking more generally e invention aims to provide a pneumatic spring which will be simple in construction and mode of operation, which will operate over long periods without loss or replacement of the erein, avoid the necessity of using metal leakages and make possi e the long continued use of the same fluid therein, and

rings minimize `bl which will adjust itself automatically to difg ferent load conditions and will absorb shocks members, having an air cushion therebe purpose of absorbing and rewithout undue rebound or hunting action.

Further objects and advantages of the invention will be in part obvious and in part speclically pointed out in the description hereinafter contained which taken in conjunction with the accompanying drawings, discloses a preferred embodiment thereof. Such embodiment thereof, however, is to be considered merely as illustrative of its principles. In the drawin l v .Fig 1 is a central longitudinal sectional view of a pneumatic spring constructed in accordance with the invention.

Fig. 2 is a transverse section taken on line 2-2 of Fig. 1 looking in the direction of the arrows.. The spring comprises in general a piston member l which is slidable in a cylinder 2, which provides a chamber3 ton and containing a-ir under pressure which serves to support the piston. When the device isvto be used to support the body of a vehicle, the hollow be provided with a cap 5 containing for one element of a universal joint (not `illustrated) while the o posite end plate 6'of the cylinder is providV with ears 7 for similar purposes. Thus the Weight of the vehicle body will rest upon the piston 1 and road inequalities will cause the piston and cylinder to slide back and forth relative to each other. Longitudinal and lateral'strains on the ve- -hicle preferably parts on the vehicle so as to relieve the air .spring from these strains.

The lower part of chamber 3 contains a suitable liquid, such as lubricating oil, and the piston and cylinder members are so constructed that as the piston moves downward on its compression stroke to reduce the size of chamber 3, the chamber is divided up into separate sections or compartments and oil is caused to flow from one compartment to the other. As shown, the bottom of chamber 3 is provided with a cylindrical head 8 suitay supported from the lower end wall of cylinder 2 and the iston member 1 is provided with anannulr downwardly progectare taken care of by otherV beneath the pisvpartment 3al 25 (hereinafter movement moves back and forth in chamber 3 above the head 8, and-thus does not cause the oil to move from one part of the .chamw ber to another; but when the spring 1s subjected to a shock or the load to be carried is increased suiciently to move member 9 downwardly pasttlie head l8, the lower .annular Compartment 3" between cylinder 2 and the head is cut olf from the remainder of chamber 3. This compartment 'contains largely oil under pressurewhilethe yremainder of the cham er contains a relatively large proportion of compressed air. The pressure in the compartment 3, due to the relatively small amount of air contained, increases rapidly when the piston enters it and may be utilized to cause oil in said compartment to flow into the remainder of chamber 3 during the compression stroke of the piston. As shown a plurality of oil passagewayslO lead from the lower part of compartment 3* through the end plate 6 of the cylinder and past a flexible packing member 11 which acts as a one-way valve, to a nozzle 12 mounted on the bottom end wall of the cylinder 2 and 4delivering into chamber 3. When member 9.

the head 8 oil from comwill therefore be forced through passageways 10 past valve 11 and through nozzle 12 into the chamber 3, at a velocity about as many times faster than the travel of the piston as the orifice in the injector is smaller than the displacement of piston extension 9 thus actuating the injector.

The valve 11 prevents any back iow of air from the nozzle into compartment 3a during return or upward strokes of the piston, tlie compartment 3a being again filled with oil when piston extension 9 is raised above head 8 on the return stroke. This will causea reduction of the pressure in compartment 3a to a pressure below that in chamber 3, causing oil to flow past the one-way packipgs 24 and described) from chamber 3 n on.

moves down past to compartment It is also possible to operate the injector above described by air or other gas, as well as by liquids, the essential condition being that the fiuid be sufn'ciently compressed in compartment 3 to flow rapidly through the injector. compartment 311 and chamber 3 is'brought about by having less elastic fiuid in the compartment in proportion to thedisplacement of the piston extension 9, than is the case in chamber 3. Y f

In order to prevent the dampeniiig action -to the spring from being too abrupt as piston extension 9 enters compartment 3a, I provide a small amount-.of air therein, which may be accomplished,for example, by a bell-like member 12a, supported from nozzle 12, and in which a small amount of air`will be trapped when the oil is initially added t0 This difference. in pressure between i jectssomewhat above the normal level of the liquid in such chamber, and is provided with throttling openings 13 to ermit a limited amount of oil to flow out om between the 'piston and head 8 as the piston'nears the head. As the piston approaches the limit of its compression stroke I also prefer Ato` segregate a portion of the oil into a confined space, to check further extreme movements of the piston. In the present form of the invention the piston slides down past the upper end of nozzle `12 when the piston' approaches the end of its compression stroke, thus confining oil between its face 14 and head 8 in such a way that the oil can escape from the confined space only very slowly through the vent holes 13. This prevents injury to the spring when subjected to severe shocks.

I also prefer to utilize the flow of oil caused n through a pair of flexible packing disks I6 which act as oneway;valves; thus as the pis-` tonaextension 9 moves downwardly a et of oil at high velocity will ow throug the nozzle and cause valves 16 to lift and the air sucked in through lsuch valves will be entrained with the oil and carried alonginto chamber 3.

The pneumatic pressure within the chamber is thus built up during the compression stroke of the piston to whatever xtent required to t be carried and sustain any increase in lo motion of the pisto assist in dampening the ton and bringing it back to normal position. It is found that a very rapid How of oil may be brought about in the manner above described which will bring about a correspondingly rapid flow of air from the low to the high pressure cushion and will act very quickly to build up the pressure in chamber 3 and thus make the spring quickly responsive to any increase in the .load to be carried. I prefer to subject the piston 1 not only to the action of a sustaining pneumatic cushion iii chamber 3 butalso to what may be termed complementary changes of pressure upon its opposite faces, whereby a building up of Ipneumatic pressure in chamber 3, for expressure acting upon the upper face of the piston and the air ports 15 draw their air from thischamber, for example, through the annu- 15 chamber 17 or 18 and which are uncovere 1,749,691 .a 1 j3 lar space 18 between cylinder 2 and a jacket drop below atmospheric `pressure f for any 19 enclosing the latter, whereb1 the s ace 18 reaaom'such as an 'abnormally high .pressure in effect constitutes a art-o cha-m r 17. chamberv 3, the packings 26 and 27' e During compression stro es of the piston 1 the `geld to permit outside air to' flowfinto cham- 5 latter 1s therefore ur ed back .to normal posir 17 tion not only by the uilding up of pressure become leaky the spring .will stillv function, in chamber 3 beneath the piston but also by4 but `without changes of pressure inchamber17 reductionin rassure inchamber 17. complementary to those produced in cham- If the loa on the piston is lightened or the ber 3.

orif the packings 26 and ;27 should:l l

- pressure in chamber 3 built up to such an ex- While a preferred embodiment of the inven 75 tent as to urge the piston up to an abnormally tion has been disclosed it will be obvious that `high, sition, the pressure in chamber 3 may many chan es may be made therein without; be religved, for instance, vby providing one departing rom its principles as defined in 'or more suitable bleed openings 20 leadln to the following claims.

gby I claim:

the piston under such conditions. The sens1- 1. A pneumatic spring comprising a pistiveness of the action of the piston may be deton member and chambers on o posite sides termined by the position of these bleed openthereof containing fluid atA dierent Ipresings; for example if the openings are placed sures, the Huid in the high pressure c amre ativel high the piston will tend to assume ber acting as a sustaining cushion and auto-' 35 a normaiposition in which the lower end of matic means for transferring iluid directly piston extension 9' does not cut olf vcompartfrom low ressure chamber` to the high resment 3l from the remainder of chamber 3 and sure cham er` upon movement of the piston under these conditions the spring will be more toward the high pressure chamber.

sensitive in its action. But if bleed openings 2. A pneumatic spring comprising a piston 90 20 be placed in a lower position, the normal member and a chamber on one side thereof, position of the piston will be such that piscontaining fiuid under pressure to form a suston extension.9 cuts oi compartment 3* from taining cushion, and means operated by the the remainder of chamber 3 more quickly and compressive force of said piston on the fluid so the pumping action of the oil occurs under in said chamber during compression strokes 95 smaller shocks, thus making the spring more to cause additional fluid to iiow into said sluggish in its movements. chamber and means for relieving said cham- The chamber17 may be connected with the ber from excess pressures. space 18 through further openings 18*l in 3. A pneumatic spring comprising a piston cylinder 2,. such openings being preferably and a chamber on one side thereof, contain- 100 positioned so as. to be covered by the piston if ing liquid and gas under pressure to form the latter should move to any extreme upper a sustaining cushion, means for causing adgosition. A certain amount of air will then -ditional liquid to flow into said chamber dure confined in chamber 17 and act as a dashing compression strokes of the pistonand pot to prevent the piston from bumping for utilizing such liquid flow to aspirate ad- 105 against the upper end wall of the cylinder. ditional gas into said chamber.

It will be noted that the same body of air 4. A pneumatic support comprising a pisis circulated around through chambers 3 and ton member and a'chamber on one side there- 18 during the action of the spring whereby of containing fluid under pressure to form neither the air nor the oil will require re- 'a sustaining cushion, said piston and cham- 110 placement aside from unavoidable leakage. ber having parts meeting to divide the cham- The leakage will also be reduced to a mlniber into separate compartments as the piston mum since the lower end 0f the oyllnder` 2 travels into the chamber, means whereby may be permanently closed from the outside iiuid is caused to iiow from said last menair, whereby there may b e no leakage through tioned compartment to the other compart- 115 packed J'Olll'tS IQID the hlgh Pressure Chamber ment during compression strokes of the pisto the outside a1r. Preferably the plStOIl l ton, said means including an injector acting 1s provided wlth iexible cup packlngs 2 1, 22 t0 cause gas t0 110W along with the fluid, and 23 't0 -prevent `leilligs past the plStOIl 5, A pneumatic Support comprising'a, pisfrom Chamber 3 t0 Chflmbel 17, and llkglg ton member and a chamber on one side of `120 from compartment 3n 1s prevented by .Slmllar the piston containing fluid under pressure to exlble CUP Packlllgs 24 and 25- It Wlllthus form a sustaining cushion, said chamber havbe Seen thft ally leakage 011i? 0f the hlgh PIeS- ing a head supported from its end wall and Sure 6115111011 must be IDQ the 10W PIQSSUYG said piston having an annular extension o0 cushion and from thence 1t 1s automatlcally adapted to move past Said head to cui; 0H a, 125 vPumpd back aS required t0 Sustain the loadcompartment from the chamber and a nozzle l The joint for the piston stem 4 may also be having a one way valve associated therewith packedl by similar iiexible cupped packings for delivering iuid from said compartment 26 and 27 held in place by .the end plate 28. to the chamber proper during compression 55 In case the pressure in chamber 17 should strokes 0f the pistou, 13

i adapted to move past said head to cut off a compartment from the chamber', a nozzle having a one way valve associated therewith for delivering fluid from said compartment A -to the chamber proper during compression and strokes of the piston said nozzle for admit-l Valve associated with ting gas thereto.

7. A pneumatic spring comprising a piston member, a chamber on one side of the piston containing fluid under pressure to form a sustaining cushion and a further chamber acting on the other side of the piston containing fluid at relatively low pressure, and means for transferring fluid frombne chamber to the other upon movement of the piston.

8. A pneumatic spring comprising a piston member, a chamber on one side of the piston containing fluid under pressure to form a sustaining cushion, a further chamber on the other side of the piston containing Huid at relatively low pressure, 'and means for transferring fluid from the chamber of relatively low pressure to the sustaining chamber upon movement of the piston towards the sustaining chamber.

9. A pneumatic spring comprisingla piston member, a chamber on one side of 't e piston containing Huid under pressure to form a sustaining cushion, a further chamber on the other side of the piston containing fluid at relatively-low pressure, means for trans` ferring fluid from the chamber of relatively low pressure to the sustaining chamber upon -movement of the piston towards the sustaining chamber and means for permitting liuid to pass from said sustaining chamber to the chamber of relatively low pressure when the piston moves a predetermined amount towards the low pressure chamber.

10. A pneumatic spring comprising a piston member, a chamber on oneV side of the piston containing liquid and gas under pressure to form a sustaining cushion, a chamber on the other side of the piston and containing gas under relatively less pressure, mea-ns for causing liquid to How into said sustaining chamber when the piston moves towards the latter,

and means whereby said flow of liquid aspirates chamber into said sustaining chamber.

11. A pneumatic spring comprising a piston and a chamber on one side thereof, containing fluid to form a sustaining cushion, -means forcausing additional fluid to flow into said chamber during compression strokes of the piston and for utilizing such liow to aspirate gas into the said chamber.

12. A pneumatic spring having a `piston a further one wayladditional fluid to said injector fluid under pressure, and imeans for circulating said fluid to aspirate additional uid into said chamber.

13. A pneumatic spring comprising apiston member and a. chamber on oneside thereof containing fluid under pressure .to form a sustaining cushion, a compartment associated with said chamber containing fluid subjected to relatively greater pressure during compression strokes ofl the piston, adapted to deliver Huid-from said compartment into the chamber, means for admitting and means for-'forcing the fluid from said compartment through said injector.

14. A pneumatic spring comprising a piston member, a chamber on one side thereof, containing fluid under pressure to form a sustaining cushion, a chamber on the other side of the piston containing fluid under relatively less pressure, means for transferring fluid from the chamber of lower pres-- sure to the higher upon movements of the piston, and means for permitting outside air to liow intol the chamber of relatively low pressure.

-15. A pneumatic spring comprising a. piston member and a chamber on one side thereof, containing liquid and gas under pressure to form a sustaining cushion, rectedinto said chamber, means whereby compressive movements of said piston ltoward said chamber cause liquid "to flow` through said nozzle into said chamber, and means for utilizing said liquid flow to aspirate, furthei` fluid into said chamber.j

In testimony that I claimvthe foregoing, I have hereunto set my hand this 21st day of April, 1925. i

f WILLIAM B.l CHAPMAN.

gas from the `low pressure sol a nozzle di- ,y 

